The present invention relates to a new and improved construction of a controlled deflection roll, also typically known in the art as a flexure adjusting roll or a roll with bending or sag compensation.
Generally speaking, the controlled deflection roll of the present development is of the type comprising a rotatable roll shell which can be rotated about a stationary and non-rotating support member or beam. The roll shell is supported relative to the stationary and non-rotating support member or beam by a plurality of hydrostatic support or pressure elements arranged next to one another or in juxtaposition in the axial direction or axial direction of extent of the roll shell. In such controlled deflection rolls, the hydrostatic support elements are movable in the supporting direction thereof, in other words, in the direction in which such hydrostatic support elements support the rotatable roll shell, and these hydrostatic support elements are tiltable to a certain or predeterminate extent about the supporting direction. Normally each of the hydrostatic support elements possess, on their bearing surface facing the roll shell, at least two bearing pockets which are offset in the circumferential direction of the roll shell. These bearing pockets are connected by a pressure-reducing bore or throttle bore in flow communication with at least one pressure chamber from which a fluid under pressure is delivered or fed to the bearing pockets. The hydrostatic support elements are typically part of a piston-and-cylinder unit which allows the pressurized fluid in one or more cylinders thereof to urge an associated hydrostatic support element towards the roll shell, and each of which cylinders simultaneously bleeds to or flow communicates with related bearing pockets thereon.
Controlled deflection rolls of the above type are disclosed, for example, in U.S. Pat. No. 3,885,283, granted May 27 1975, and may be used in a press device or rolling mill so that, together with at least one back-up or counter roll, a web of material guided between both of these rolls can be subjected to a continuous and predictable pressure treatment.
As a result of the movement of the hydrostatic support elements in the roll shell-supporting direction in this kind of press device, the roll shell of the controlled deflection roll does not actually bend or adapt to the back-up or counter roll, so that there is attained a uniform pressing force or pressure or a pressing force or pressure with a desired force or pressure profile between the two rolls over their entire width, in other words, in the cross-machine direction. When a pressing force or pressure is exerted, only the stationary support member of the controlled deflection roll bend or deflects, but not, however, the roll shell. The inclination or bowing of the stationary support member relative to the roll shell is taken-up by the tilting capacity or capability of the hydrostatic support elements about the supporting direction, so that the hydrostatic support elements cannot bind or jam.
In this type of press device, a one-sided tilting moment is exerted on the hydrostatic support elements during the operation of the controlled deflection roll in the travel or running direction of the pressed or rolled material web, i.e. in the circumferential direction of the roll shell. In the controlled deflection roll disclosed in the aforementioned U.S. Pat. No. 3,885,283 an attempt was made to achieve a stable or equilibrium position in the pressing direction by the provision of several pressure pockets arranged next to one another on the bearing surface and which were connected to the same pressure chamber or compartment. Nonetheless, it was thought to be necessary to design the hydrostatic support elements in such a way that they were also tiltable in the circumferential direction in order to take-up or absorb this additional tilting moment; i.e. the hydrostatic support elements were made tiltable in all directions.
Notwithstanding the above, those skilled in this technology subsequently took the view that special measures were necessary to avoid the tilting of the hydrostatic support elements in the circumferential direction of the roll shell, as is apparent from British Patent Specification No. 2,143,302, published Feb. 6, 1985 or U.S. Pat. No. 4,520,723, granted June 4, 1985. To achieve this result, there was proposed separate control of the pressure in the bearing pockets located next to one another or in juxtaposition in the circumferential direction by means of suitable positioning sensors. For this purpose, the bearing pockets were connected to separate pressure chambers or compartments which, in turn, were separately supplied with a pressure medium at a different pressure.
The construction or design of the hydrostatic support element in such a manner that it is tiltable in all directions, necessitates a complicated shape or configuration of the piston-and-cylinder guide structure or unit, which increases the manufacturing costs and requires certain close tolerances to be adhered to for reliable operation. The separate control of the pressure in the adjacent pressure pockets also requires a complicated, expensive and trouble-prone control system.